Ferroelectric liquid crystals are generally known as being liquid crystals that exhibit smectic phases. These liquid crystals are used in image-producing displays by utilizing the properties that it possesses spontaneous polarization and that the direction of the spontaneous polarization changes under the influence of an external electric field.
It is reported by N. A. Clark, and S. T. Lagerwall, Appl. Phys Lett, Vol. 36, 899 (1980), that liquid crystal electro-optical devices using ferroelectric liquid crystals have memory characteristics and are capable of fast response. Ferroelectric liquid crystals (FLCs) are widely used in spatial light modulators, light shutters, optical inter-connects, optical switches, optical gates for optical computing, high definition television terminals, electro-optic modulators, display devices etc. Among all parameters of FLCs, the memory effect or the bistability is of primary concern because of its applications in personal computers, personal digital assistant, digital cameras etc. and having tremendous potentiality for low cost, large area, high speed, and high density memory needed for future computers. The fast switching bistable electro-optic devices based on FLC material comprises a well aligned thin (1-3 μm) layer of FLC sandwiched between two optically flat polished glass plates having transparent electrically conducting electrode patterns thereon. The two glass plates are peripherically sealed and the electrical connections are taken out from the substrates. The display fixed with crossed polarizers on outer faces of both glass plates is connected with very large scale integrated (VLSI) electronic modules to be used as an information display for displaying electrical or optical data.
At present, memory devices are based on:
1. Materials other than liquid crystals e.g. solid ferroelectrics, polymer etc.
2. Ferroelectric liquid crystal in surface stabilized geometry
3. Liquid crystal composite
4. cholesteric liquid crystal polymer
5. Organic ferroelectric layer and
6. Polymer dispersed liquid crystals